Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS

From:

Samuel Thibault

Subject:

Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS

Date:

Fri, 27 Mar 2009 11:36:28 +0100

User-agent:

Mutt/1.5.12-2006-07-14

Avi Kivity, le Fri 27 Mar 2009 13:02:49 +0300, a écrit :
> Samuel Thibault wrote:
> >Nothing in Linux makes filesystems and devices systematically read/write
> >the amount of data that was requested.
>
> We're talking about the qemu block layer, not Linux.
Well, in the part I quoted before my sentence:
> At least for Linux I couldn't think of a way to introduce such an
> arbitrary limit anyway.
I believed you were talking about Linux never making short reads.
> You're proposing to take the posix API rules and apply them to the
> qemu block layer.
No. I'm proposing to take into account that because of the posix API
rules, we should fix our block layer.
> But posix read/write does not fit how DMA works. A request should
> either complete fully, or fail, leaving the destination (disk or
> memory) in an undefined state.
Sure. Again, please read what _I_ wrote: I'm not proposing to expose
that into DMA, just make it genericly handled in the block layer.
Samuel